The installation of electrical devices, such as circuit breakers, in switchboard and panelboard compartments is generally of two types. In one type of installation, circuit breakers are essentially stationary mounted to structural members or frame of the switchboard, typically with terminal electrical connection effected via bolted joints. Alternatively, circuit breakers may be physically supported solely by the switchboard bus-work via these bolted terminal joints. In such stationary installations, inspection and maintenance of the circuit breaker is difficult and quite hazardous if attempted while the switchboard is live. The terms "switchgear" herein describes the combination of the draw-out circuit breaker and the compartment whereas the term "switchboard" refers to the compartment, per se. In some situations, the hazards must be assumed, since de-energization of the switchboard and thus interruption of electrical service to all of the branch circuits in the switchboard cannot be tolerated. To reduce the hazards of working with live switchboards, devices are provided with plug-in or stab-type primary disconnect contacts which do not require direct contact and manipulation to effect their connection and disconnection with mating disconnect contacts of the switchboard compartment. Thus the device, e.g., circuit breaker, can be plugged in and unplugged from a live switchboard in relative safety.
In higher current applications, the circuit breakers are physically large and quite heavy, thus rendering the bodily movement of the circuit breaker necessary to electrically connect and disconnect it from the switchboard cumbersome if not impossible, unless mechanical assistance is afforded. Not only does the weight and bulk of the circuit breaker become difficult for the electrician to handle, but, as the current ratings increase, the contact pressures of the primary disconnect contacts become extremely difficult, if not impossible to overcome. To surmount these problems, so-called "draw-out" apparatus has been resorted to for both supporting the circuit breaker and affording mechanical assistance in overcoming the extreme contact pressures of the disconnect contacts.
Draw-out apparatus are typically designed to support the electrical device for racking movement between an extended position well out of a compartment and an engaged position within the compartment where the load current carrying primary contacts of the device and compartment are fully engaged. Since electrical devices, such as circuit breakers for industrial applications, are typically equipped with a variety of accessorial functions served by external auxiliary circuits, provisions must be made for making and breaking these auxiliary circuits as the device is moved between its extended and engaged positions. To this end, so-called mating secondary disconnect contacts are mounted with the device and the compartment. These secondary disconnects are engaged while the device is in the engaged position and become disengaged at some point during movement of the device out to the disengaged position. It is common practice to provide a test position for the device intermediate its engaged and extended positions where the primary contacts are separated but the secondary contacts are still engaged. In this test position, the accessorial functions can be thoroughly tested in safety while the device itself is not electrically connected.
It is understandably important that the operator of the draw-out apparatus be constantly aware of the position of the device relative to the compartment for his own safety as well as that of the equipment. To this end, position indicators are utilized to display or otherwise indicate the position of the device relative to the compartment. U.S. Pat. No. 4,011,424 entitled "Position Indicator for Draw-out Apparatus" describes the operation of switchgear apparatus in great detail. U.S. Pat. No. 2,768,254 entitled "Draw-out Switchgear Mechanism" describes the transfer assembly for allowing the movement of the switchgear in and out of the switchgear compartment. A description of a state-of-the-art secondary disconnect arrangement for draw-out circuit breakers is found in U.S. Pat. No. 5,594,221 entitled "High Ampere-Circuit Breaker Secondary Disconnect Arrangement".
With such existing draw-out devices, the operator usually relies on an estimate of the distance that the circuit breaker has moved within the compartment by means of a line painted on the rails that carry the circuit breaker while he or she continues to operate the threaded crank that moves the circuit breaker into the compartment. In the event the operator continues to operate the crank after the circuit breaker plug connectors have made contact in the completely engaged position, possible damage to the transfer assembly could occur.
Accordingly, one object of the invention is to provide visible indicia of the exact transfer status of an industrial-rated circuit breaker relative to the circuit breaker compartment to allow an operator to view the true position of the circuit breaker electrical power connectors and the secondary disconnects, at all times.